1. Technical Field
The present invention relates in general to an improved data processing system and in particular to an improved data storage subsystem for use with a data processing system. Still more particularly, the present invention relates to an improved method and system for enhanced data management within a data storage subsystem which utilizes redundant arrays of disk memory devices.
2. Description of the Related Art
Modern computer systems often use a plurality of storage devices or memories in order to store data associated with that computer. Many such storage devices are categorized as so-called "direct access storage devices" (DASD) in that the access plan for data within such a device is effectively independent of the location of the data. One example of such a storage device is a magnetic disk drive memory.
As over all system processing speeds within modern computer systems increase, magnetic disk storage technology access times have lagged. As a consequence, several techniques have been proposed for increasing the data throughput for storage systems associated with computer systems. One such technique is the provision of a redundant array of disk memory devices. Such arrays are increasingly utilized as a result of the decreases in size and cost per megabyte for data storage within disk memory devices.
One technique for providing a redundant array of disk memory devices is the so-called "Redundant Array of Inexpensive Disks" (RAID) wherein a tightly coupled plurality of disk storage devices are arranged into an array to provide greater data throughput. These disk arrays provide a high data reliability and availability. That is, the expected time to data loss is quite long and the time spent repairing systems and recovering lost data is a small fraction of total time.
However, as is well documented in the available literature on RAID systems, the notion of redundancy can carry with it a necessary acceptance of a performance degradation as a price to be paid for significantly higher levels of availability. This performance degradation occurs as a result of the need to read parity and write both data and parity whenever an application updates data. Consequently, numerous systems for organizing data and parity within arrays of disk memory devices have been proposed in an effort to increase the access performance for such systems. However, such increased performance typically occurs in response to a substantial increase in the cost of the system, as a result of the necessary provision of mirrored disk drives or the like.
It should therefore be apparent that a need exists for a method and system for enhanced data management within a data storage subsystem which utilizes redundant arrays of disk memory devices wherein access performance degradation associated with such arrays may be minimized.